scholarly journals Phenyl-cyclopentadienyl rule

2012 ◽  
Vol 31 (1) ◽  
pp. 1 ◽  
Author(s):  
Jelena Đurđević ◽  
Ivan Gutman
Keyword(s):  
Membered Ring ◽  
General Regularity ◽  
Dft Methods ◽  
Carbon Bond ◽  
Ring Currents ◽  
Carbon Carbon Bond ◽  
Cyclic Conjugation ◽  
High Level ◽  
Derivatives Of ◽  
Ab Initio Dft

Within a systematic study of cyclic conjugation in the benzo-annelated derivatives of acenaphthylene and fluoranthene, a general regularity was discovered, named phenyl-cyclopentadienyl rule (PCP rule). According to this rule, six-membered rings connected to the five-membered ring by a single carbon-carbon bond increase the magnitude of cyclic conjugation in the five-membered ring. The greater the number of such six-membered rings is, the stronger the cyclic conjugation in the five-membered ring. The PCP rule was initially established by studying the energy effects of individual rings, and was eventually corroborated by a variety of other independent approaches (Wiberg bond orders, carbon-carbon bond lengths calculated by high-level ab initio DFT methods, multicenter delocalization indices, ring currents).

On the π-Electron Content of Bonds and Rings in Benzenoid Hydrocarbons

2004 ◽  
Vol 59 (4-5) ◽  
pp. 295-298 ◽  
Author(s):  
Ivan Gutman ◽  
Tetsuo Morikawa ◽  
Susumu Narita
Keyword(s):  
Bond Order ◽  
Membered Ring ◽  
Electron Content ◽  
Bond Orders ◽  
Double Bonds ◽  
Benzenoid Hydrocarbons ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Carbon Carbon Bonds ◽  
Single Bonds

The Pauling bond order can be viewed as a measure of the π-electron content of the respective carbon-carbon bond. In benzenoid hydrocarbons its values lie between 0 (in the case of essential single bonds) and 1 (in the case of essential double bonds). If the benzenoid molecule does not possess essential single and double bonds, then the Pauling bond orders are greater than 0 and less than 1, but may assume values arbitrarily close to 0 and 1. The π-electron content of a ring is equal to the sum of the π-electron contents of the carbon-carbon bonds forming this ring. We show that in benzenoid hydrocarbons the π-electron content of any (six-membered) ring lies between 0 and 5.5. If the molecule does not possess essential single and double bonds, then the π-electron content of any ring is greater than 0 and less than 5.5, but may assume values arbitrarily close to 0 and 5.5.

Tetracarbonyl ferrate derivatives of (η6-arene)Cr(CO)3: new reagents for carbon–carbon bond formation

1988 ◽  
pp. 280-282 ◽  
Author(s):  
Joseph A. Heppert ◽  
M. Elizabeth Thomas-Miller ◽  
Paul N. Swepston ◽  
Michael W. Extine
Keyword(s):  
Bond Formation ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Derivatives Of

scholarly journals Organocatalysis for the Asymmetric Michael Addition of Cycloketones and α, β-Unsaturated Nitroalkenes

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1004
Author(s):  
Jae Ho Shim ◽  
Byung Kook Ahn ◽  
Ji Yeon Lee ◽  
Hyeon Soo Kim ◽  
Deok-Chan Ha
Keyword(s):  
Nitro Group ◽  
Michael Addition ◽  
Primary Amine ◽  
Bond Formation ◽  
Hydrogen Bond Formation ◽  
Carbon Bond ◽  
Chiral Diamine ◽  
Asymmetric Michael Addition ◽  
Carbon Carbon Bond ◽  
High Level

Michael addition is one of the most important carbon–carbon bond formation reactions. In this study, an (R, R)-1,2-diphenylethylenediamine (DPEN)-based thiourea organocatalyst was applied to the asymmetric Michael addition of nitroalkenes and cycloketones to produce a chiral product. The primary amine moiety in DPEN reacts with the ketone to form an enamine and is activated through the hydrogen bond formation between the nitro group in the α, β-unsaturated nitroalkene and thiourea. Here, the aim was to obtain an asymmetric Michael product through the 1,4-addition of the enamine to an alkene to form a new carbon–carbon bond. As a result, the primary amine of the chiral diamine was converted into an enamine. The reaction proceeded with a relatively high level of enantioselectivity achieved using double activation through the hydrogen bonding of the nitro group and thiourea. Michael products with high levels of enantioselectivity (76–99% syn ee) and diastereoselectivity (syn/anti = 9/1) were obtained with yields in the range of 88–99% depending on the ketone.

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